Proper drainage is an important consideration in the design and construction of subterranean walls. In the absence of proper drainage, hydrostatic pressure can result in severe structural damage, weakening walls and causing leaking conditions.
The problem of proper drainage has been addressed historically through the use of well known aggregate drainage systems with resultant costly and time consuming installation. In recent years, solutions have been sought through the utilization of a subterranean wall drain system comprising a generally horizontally disposed drain pipe having openings therein and a generally vertically disposed longitudinal planar core defining channels normal to the pipe with water pervious sheet material covering at least the core and the openings in the pipe to form a filter therefor. Such systems are exemplified in U.S. Pat. Nos. 3,563,038 and 3,654,765, issued in the names of Kent A. Healy and Richard P. Long, entitled respectively "Subterranean Drain" and "Subterranean Wall Drain".
The Healy/Long patents provided a prefabricated drainage system adopted for use in a variety of soil conditions and types. The system is less costly than prior art systems since it provided a prefabricated unit which can be installed easily and by relatively unskilled personnel.
Others have followed the Healy/Long concept in providing alternate specific designs. One of these prior art designs is shown in the drawings in FIGS. 1A and 1B, labeled "prior art". The drain shown in FIGS. 1A and 1B has continuous intersecting walls 10 formed by depressions 12 on each side running in directions generally angular to its vertical and horizontal edges. Raised mountains 14 are formed at the intersections of the walls 10. On one side the mountains support a filter fabric 16 and on the remaining side abut the structure being protected so that the member is in spaced relationship thereto. Although this design has been successful, improvements can be made thereon.